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SPIRou / Infrared SpectroPolarimeter

2016 August: Integration of the SPIRou Parabola

The SPIRou off-axis parabola was integrated on its mount at LAM

Parabola delivery

Bonding of the top flexure in Invar on
the mounted Parabola
(©ZChallita-IRAP/OMP)

To minimize stresses at cryogenic temperatures, NRC-H designed a custom mount for the SPIRou parabola, with the mirror attached via three Zerodur pucks and one Invar flexure screwed on the mount. The mounting operation consists in (i) bonding three Zerodur pucks to the mirror edges, then (ii) positioning the parabola on its mechanical mount via the pucks and finally (iii) bonding the Invar flexure on the top puck. The glue is a two-part epoxy resin component (Armstrong A-12 epoxy resin adhesive) used for cryogenic applications.

For bonding the Zerodur pucks, the mirror is positioned on a specific jig allowing a perfect centering of the pucks with respect to the optical center (see Fig).  After curing, the parabola is attached to its mount through the pucks. In particular, the top puck is maintained by an Invar flexure ensuring a nominal mirror position at both ambient and cryogenic temperatures. This flexure is glued on the pucks via fifteen small pads, using fishing lines as gauges to ensure a nominal glue thickness of 0.1 mm.

Gluing and mounting were carried out at LAM (Laboratoire d’Astrophysique de Marseille) by Vlad Reshetov from NRC-H and Zalpha Challita from IRAP/OMP, using the LAM facilities and with precious help from the LAM staff.

Parabola gluing

Zerodur pucks glued on the Parabola using a specific jig
(©ZChallita-IRAP/OMP)

Parabola mounting

Parabola integration on its mount at LAM
(©ACaillat-LAM)

Parabola gluing

The Invar flexure bonding using fishing-lines as thickness gauges
(©ACaillat-LAM)

Parabola mounted

The Parabola integrated on its mount
(©ZChallita-IRAP/OMP)